Because motorcycles have a characteristic that the motorcycle is leaned to make turns, the portion of the tire of the motorcycle which contacts a road surface shifts due to the lean of the body of the motorcycle. Further, when the motorcycle is upright, the velocity of the motorcycle is high and a braking force and a driving force in the front-back direction (equatorial direction of the tires) are applied. On the other hand, when the motorcycle turns with the body of the motorcycle leaned, a lateral force is mainly applied and the velocity of the motorcycle is decreased. Thus, the tread of the tire at a center portion and the tread of the tire at a shoulder portion are utilized differently. Particularly, the enhancement of grip ability of the tires of a bike when the bike is largely leaned is demanded by general consumers, and riders who participate in races.
From the above-described perspective, for example, Patent Documents 1 and 2 disclose the technology which improves the grip ability of the tire that is provided with a reinforcement comprising a reinforcing cord spirally wound at an angle approximately along the tire circumferential direction, that is, a spiral belt, by placing a soft rubber at the portion (tread end side) which contacts a road surface when the body of the motorcycle largely leans. In these patent documents 1 and 2, desired characteristics of the tire are allowed to appear by dividing the tread portion along the width direction into three sections, that is, a center section and shoulder sections on either side of the center section, and changing the hardness, modulus of elasticity, or the like of each section of the tread rubber.
Patent Document 1: Japanese Unexamined Patent Application Publication No. H07-108805 (Claims, etc.)
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-158910 (Claims, etc.)